Saw For Blade Having Deformable Lock Teeth

ABSTRACT

A surgical saw comprises a body, a coupling assembly, and a motor. The coupling assembly is mounted to the body and adapted to releasably hold a saw blade. The coupling assembly includes an anvil, a press, and a clamping assembly. The anvil has a channel or a press foot. The press has the other of the press foot and the channel. The press foot is receivable by the channel. The clamping assembly selectively moves the press and the anvil towards and away from each other. When the press is brought towards the anvil, the press foot may press a lock tooth of the saw blade into the channel so that the lock tooth is compressed between the anvil and the press to coin the lock tooth. The motor, internal to the body, is connected to the coupling assembly to reciprocate the coupling assembly and the saw blade.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/679,554, filed Aug. 17, 2017, which is a continuation ofPCT/US2016/018289, filed Feb. 17, 2016, which claims priority to and allthe benefits of U.S. Provisional Patent Application Ser. No. 62/118,336which was filed on Feb. 19, 2015, the entire contents of which arehereby incorporated by reference.

FIELD OF THE INVENTION

This invention generally relates to surgical saws and the complementaryblades used with the saws. The invention relates to a saw and a bladewith complementary features that deform the blade when the blade ismounted to the saw.

BACKGROUND OF THE INVENTION

A powered surgical instrument, a surgical tool, used with some frequencyis the powered surgical saw. This type of instrument is used to removetissue, including bone and cartilage. Attached to the saw is a sawblade. A drive assembly internal to the saw reciprocates the blade in aback and forth motion. Often the saw includes a moving head. The head isthe component of the saw to which the blade is mounted. Some blades areconstructed to pivot back and forth, oscillate, in the plane in whichthe blade is oriented. This type of blade is referred to as a sagittalsaw blade. A sagittal saw blade is provided with teeth that extendforward from the distal end of the blade body.

Many sagittal saws and their complementary blades are designed so thatthe blade extends distally forward of the blade head. One such assemblyis disclosed in the Applicant's U.S. Pat. No. 8,100,912/PCT Pub. No. WO2007/011542, the contents of which are incorporated herein by reference.This type of saw and blade are used to remove a section of bone. This isperhaps the most common type of sagittal saw.

A surgical saw includes an assembly for removably holding the blade tothe saw. This is because the blade is often the single use component ofthe combined saw and blade assembly. One reason the blade is used onceis that upon use of the blade, the teeth are immediately dulled. Owingto the economics, it is often more cost effective to use a new bladewith each patient than go to the expense of sterilizing and resharpeninga previously used blade.

A surgical sagittal saw is typically formed so that the head has a slot.The slot is the void space dimensioned to receive the proximal end ofthe blade. Often, the proximal end of the blade is provided with one ormore openings. Each opening is dimensioned to receive a pin that ismoveably mounted to the saw head. The seating of the pin in the bladeopening releasably holds the blade to the head.

It is common practice to collectively dimension the saw head and bladeso the slot facilitates the close slip fitting of the blade in the slot.This dimensioning facilitates the relatively easy insertion of the bladeinto the saw head and removal of the blade from the saw head. A resultof this component dimensioning is that within the slot, there is smallclearance between the blade and the interior surfaces of the saw headthat define the slot. This means that within the slot the blade hasspace to move.

Owing to this tendency of the blade to move, the back-and-forth movementof the blade is not always in phase with the back-and-forth movement ofthe saw head. This out of phase movement occurs because when the sawhead reverses direction, owing to the blade having a momentum in theopposite direction, the blade continues to move in the first direction.Thus, there may be times in the movement of the saw head and blade wherethese two components move in the opposed directions. This can result inthe blade striking an adjacent surface of the saw head. This action issometimes referred to as blade slap. A result of blades continuallyslapping against the saw head is that the material forming the head canfatigue. This component fatigue can result in the fracturing of the sawhead. Once such a fracture occurs, at a minimum, it is necessary toreplace the saw head.

The failure of the blade to move completely in unison with the saw headcan even result in problems even when the blade does not strike the sawhead. The lagging movement of the blade relative to the saw head issometimes referred to as backlash. As a result of this movement eachtooth of the blade may not, in a single phase of a single oscillatorycycle, move in an arc of sufficient length. More particularly, for ablade to efficiently function, during a single phase of movement, atooth of the blade should move at least as far as the starting positionof the adjacent tooth at the start of the phase. For example, when ablade sweeps right, a tooth should move to the right a sufficientdistance so that, at the end of the sweep, the tooth will have moved toat least the location at which the adjacent tooth to the right of theblade was located at the start of the sweep. When a tooth engages inthis degree of arcuate movement, there is high likelihood that, in thesingle sweep the tooth will have sheared away the bone located betweenthat tooth and the adjacent right located tooth. This removal of all thebone between the teeth is what facilitates the efficient formation ofthe cut.

The problem arises because, owing to the backlash, the saw blade and byextension the teeth of the saw, in a single phase of movement, engagesin an arcuate movement that is less than the arcuate movement of the sawhead. In some situations that means that in the single phase ofmovement, a blade will not sweep to the location at which the adjacenttooth was located at the start of the sweep. When this event occurs, notall the bone between the teeth are sheared, cut away. This can reducethe efficiency of the cutting process.

In addition to the blade moving side to side relative to the saw head, ablade may be able to move up and down relative the head slot in whichthe blade is seated. This movement is sometimes referred to as the outof plane oscillation of the blade. Alternatively, this movement issometimes referred to as blade whip. This out of plane movement of theblade relative to the saw can adversely affect the precision of the cutformed by the blade. This movement can also stress both the saw head andthe proximal end of the blade, the portion of the blade seated in thesaw head slot. The stressing of the saw head can result in thefracturing of the saw head. The stressing of the proximal end of theblade can result in the deformation of the blade. This deformation canalso reduce the precision of the cut made by the blade.

Another disadvantage of this movement of the blade relative to the sawhead is that it can result in the blade moving to a less than optimalposition for the procedure being performed. When a sagittal saw is usedto remove a large section of the bone such as a portion of the knee, theblade is often placed in a resection guide. This instrument is a blockthat is affixed to the bone adjacent where the cut is to be formed. Theblock is formed with one or more slots. The slots serve as guide pathsthrough which the saw blade is inserted. By cutting the bone along theguide paths defined by the slots, the bone left after the cut will havethe desired shape. This precision shaping of the bone ensures the properfitting of an orthopedic implant to the bone. Owing to the flexure ofthe blade when fitted in one of these slots, the blade can gall, wearthe material that defines the slots. This can result in the shape of theslot deforming from the shape needed to ensure that a cut formed basedon the shape of the slot has the desired shape. Once this deformation ofthe resection guide occurs, the guide is no longer useful.

There is therefore a desire to provide a surgical sagittal saw andcomplementary blade that are constructed so that, when the saw and bladeare actuated, the saw head and blade move as a single rigid structure.One means to ensure the saw head and blade move as a single rigid bodyis to provide a clamping assembly that, when set, applies an appreciableamount of force to the blade to hold the blade to the saw head. Thistypically means that the individual charged with blade insertion andblade removal needs to apply a significant amount of force in order toreset and release the clamping assembly. Requiring the individualresponsible to perform these tasks to apply these forces can complicatethe process of inserting and removing the blade. Requiring theindividual to apply these forces can also slow the processes associatedwith both inserting and removing the blade. This is especially true ifthe individual has limited arm and hand strength. Further, if theseforces are not properly applied, especially the force required to setthe clamping assembly, the blade may not be fully locked to the sawhead. When the saw is actuated this could result in a clearlyundesirable event, the blade working free from the saw.

SUMMARY OF THE INVENTION

This invention is related to a new and useful surgical saw andcomplementary blade for use with the saw. The saw and complementaryblade of this invention are designed to ensure that, when the blade isremovably attached to the head integral with the saw, the blade and sawhead move as a single unit.

The blade of this invention is provided with one or more lock teeth. Thelock teeth are formed from material that, in comparison to the materialfrom which the blade body and cutting teeth are formed, is relativelysoft.

The saw of this invention includes a head. The head includes an anviland a press. The press is located adjacent the exposed surface of theanvil and is moveable towards and away from the anvil. At least one ofthe anvil or the press is formed to define one or more slots. Each slotis dimensioned to receive a separate one of the blade lock teeth. Thepress or the anvil is formed with press surfaces. The press surfaces arein registration with the slots formed in the other of the anvil or thepress.

To removably mount a blade to the saw according to this invention, thepress is first moved away from the anvil. The blade is placed betweenthe anvil and the press so the one or more lock teeth seat in thecomplementary slots formed in the anvil or the press. The press is movedagainst the blade. More specifically, the press is displaced so thatblade is compressed between the anvil and the press. As a result of thiscompression of the blade, the press surfaces push the lock teeth intothe slots formed in the anvil or the press.

As a result of the lock teeth being pushed into the adjacent slots andthe lock teeth being relatively soft, ductile, the lock teeth aredeformed. Each lock tooth is deformed, becomes coined, around thesurfaces of the anvil and the press that define the slots and the presssurfaces. As a result of this deformation of the blade lock teeth, thereis essentially no clearance between the lock teeth and the anvil and thepress. The saw head and blade essentially become a single piececomponent. There is essentially no movement of the blade relative to thesaw head.

In some versions of the invention, the blade lock teeth are furtherformed to have opposed faces. At least one tapered surface extendsbetween the opposed faces. The tapered surfaces are the surfaces of thelock teeth that are disposed against the corners, the edges, of the sawhead that define the slots and press surfaces. The portions of the lockteeth that define the tapered surfaces, during the process of lockingthe blade to the saw head, are the portions of the lock teeth that arecoined.

In some versions of the invention, the press is a cap that is disposedover the anvil.

In some versions of the invention, the blade has plural sections. Thesections of the blade that defines the one or more lock teeth arerelatively soft. The remaining section of the blade, the section thatdefines the cutting teeth, is relatively hard. In some processes used tomake this version of the invention, the stock from which the blade isformed is manufactured out of relatively hard material. The blade isselectively treated so as to result in the lock teeth being softer, moreductile, than the rest of the blade. In some processes used to make thisversion of the invention, the stock from which the blade is formed isrelatively soft. More specifically, the stock is sufficiently ductile sothat when pressure is applied to the lock teeth, the lock teeth willdeform.

In some versions of the invention wherein the blade is formed out ofmaterials of different hardnesses, the section of the blade defining thelock teeth is formed from a first material that is relatively soft. Themajority, if not all of the rest of the blade is made out a material ofsufficient hardness that it can cut the bone the blade is intended tocut.

In some versions of the invention, the proximal end of the blade isprovided with a circularly shaped void. In some versions of thisinvention, at least one lock tooth extends inwardly from the perimeterof this void. In many versions of the invention, plural lock teethextend inwardly into this void.

The saw and blade of this application may be designed as sagittal saws,oscillating saws or reciprocating saws. Also, for the purposes of thisinvention, a rasp is considered a type of saw blade.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is pointed out with particularity in the claims. The aboveand further features and advantages of this invention are understoodfrom the following Detailed Description taken in conjunction with theaccompanying drawings in which:

FIG. 1 is a perspective view of a saw assembly of this invention;

FIG. 2 is a cross sectional view of the saw assembly;

FIG. 3 is an exploded view of the saw assembly;

FIG. 4 is a cross sectional view of the distal end of the body of thesaw unit of this invention including the head and neck;

FIG. 5 is a perspective view of the drive link;

FIG. 6 is a perspective view of the pivot sleeve;

FIG. 7 is a cross sectional view of the pivot sleeve;

FIG. 8 is a cross sectional view of the bearing assembly to which thepivot sleeve is mounted;

FIG. 9 is a perspective view of the top of the cap;

FIG. 10 is a perspective view of the bottom of the cap;

FIG. 11 is a plan view of the blade of this invention;

FIG. 11A is a plan view of an alternative construction of the blade ofthis invention;

FIG. 12 is a cross sectional view of the blade taken along line 12-12 ofFIG. 11;

FIG. 13 is a cross sectional view depicting the relative location of thesaw unit anvil and press and the saw blade prior to the locking of theblade;

FIG. 14 is a cross sectional view depicting how, when the blade islocked, a blade locking tooth is deformed, coined, by the anvil andpress;

FIG. 15 is a plan view depicting the positions of the cap feet againstthe blade when the saw unit is in the run state;

FIG. 16 is a side view of an alternative saw unit of this invention;

FIG. 17 is a cross sectional view of the blade locking tooth of analternative blade of this invention;

FIG. 18 is a plan view of an alternative blade, specifically areciprocating blade, constructed in accordance with this invention;

FIG. 18A is a plan version of an alternative construction of the versionof the blade of FIG. 18, wherein the blade is constructed to function asa rasp;

FIG. 19 is a plan view of a second alternative blade of this invention;and

FIG. 20 is a flow chart of the process steps that are executed tofabricate a blade of this invention;

FIG. 21 is a plan view of the proximal end of a blade formed accordingto the method of FIG. 20.

DETAILED DESCRIPTION

FIGS. 1 and 2 depict a surgical saw assembly 30 constructed inaccordance with this invention. Saw assembly 30 consists of a saw unit40 and a blade 140. The depicted saw assembly 30 is what is referred toas a micro sagittal saw. This saw is used to perform procedures on smallbones. Examples of bones on which a micro surgical saw is used toperform surgery on include: the skull; the spine; the hand; and thefoot. Internal to the saw assembly 30 is a motor 62 represented by aphantom cylinder. Motor 62 includes a rotating shaft 64 represented by asmaller diameter phantom cylinder. The actuation of the motor 62 resultsin the back and forth oscillations of the blade 140. More specifically,the blade 140 pivots back and forth around an axis that extends throughthe plane of the blade.

Saw unit 40 includes a saw body or shell 42, seen best in FIGS. 2 and 3,that houses or holds the other components of the saw unit. Body 42 has agenerally cylindrical main section 44. Body main section 44 isdimensioned to be held in the hand. Typically, the saw body 42 is heldbetween the thumb and forefinger or between the thumb and middle finger.Extending distally forward of the main section, the saw body 42 has aneck 46. (“Distally” is understood to mean away from the surgeon;towards the site on the patient to which the blade 140 is applied.“Proximally” is understood to be towards the surgeon holding the sawunit 40; away from the site on the patient to which the blade 140 isapplied.) The saw body 42 is dimensioned so that the neck 46 is, inplanes perpendicular to the proximal-to distal longitudinal axis alongthe body, generally semi-circular in cross section. Saw body 42 isfurther dimensioned so that the outer surface of the neck 46 is locatedradially inward from the outer surface of the body main section 44.Forward of and integral with the neck 46, the saw body 42 has a head 48.In the depicted version of the invention, head 48 has a shape of a slicesection of a sphere. More particularly, saw head 48 has a shape in whicha first surface is along a plane that extends slightly above themid-plane of the sphere. A second surface that is parallel to the firstsurface is located closer to what would be one of the poles of thesphere defined by the head 48. Saw body 42 is further shaped so that thehead 48, relative to the longitudinal axis through the body 42, extendsoutwardly of the neck 46.

The saw body 42 is further formed so there is void space 52 internal tothe body main section 44 as seen in FIG. 4. The distal end of the bodymain section 44, has an opening, opening not identified. Saw body 42 isfurther formed so there is a recess 54 in the neck 46. Owing to theopening in the distal end of the body main section 44, body void space52 and recess 54 are contiguous. Saw body 42 is further formed so thatsaw head 48 has a bore 56 that extends through the head. The saw body 42is formed so that bore 56 extends along an axis perpendicular to thelongitudinal axis through the body. The distal end of recess 54 opensinto bore 56.

Returning to FIG. 1 it can be seen that motor 62 is disposed in voidspace 52 internal to the body main section 44. Motor 62 is oftenelectrically driven. A cable 60 extends proximally from the proximal endof the body 42. Cable 60 is connected to a control console notillustrated and not part of the present invention. The control consolesupplies energization signals over cable 60 to the motor 62 that actuatethe motor. Not shown are the connections between the individualconductors internal to the cable 60 to the motor 62.

A drive link 66, seen best in FIGS. 2, 3 and 5, is pivotally mounted tothe saw body head 48. The drive link 66 includes a cylindrical stem 68.Forward of stem 68, the drive link 66 has a head 70 that isapproximately disk like in shape. More specifically, drive link head 70has two opposed surfaces 72 that are planar and parallel. In FIG. 5, onesurface 72 is fully illustrated and the edge of the opposed surface 72is called out. The perimeters of surfaces 72 are generally circular inshape. The outer diameter of the head 70 is generally equal to the outerdiameter of the widest portion of body head 48. In the depicted versionof the invention, the distal end of body head 48 is truncated. Thus, themost distally directed surface of the head 70 is a flat 76. Flat 76 ispresent for manufacturing reasons and is otherwise not relevant to thisinvention.

The drive link 66 is further formed to have a hole 77 that extendsbetween the link major surfaces 72. Hole 77 is circular in shape and isconcentric with the axis of the link head 70 that extends between themajor surfaces 72. The drive link 66 is further formed to have fourarcuate islands 78, two islands identified, that extend upwardly fromthe head major surface 72 that is directed away from saw body head 48.The islands 78 are located adjacent the outer perimeter of hole 77 andare arcuately shaped. Each island 78 is arcuately spaced from theadjacent islands 78. Thus, between each pair of islands 78 there is anisland void, i.e., a channel 80, (two channels identified).

A pivot pin 84 and a bearing assembly 92 rotatably hold the drive link66 to the body head 48. The pivot pin 84, as seen in FIGS. 6 and 7, hasan elongated cylindrical stem 86. Stem 86 is dimensioned so that the topof the stem, as seen in FIG. 3, can be press fit or otherwise secured inthe hole 77 formed in the drive link head 70. The components forming thesaw unit 40 are further dimensioned so that the pin stem 86 has adiameter less than the diameter of the saw body head bore 56. Pin 84 isfurther formed so that at the end of the stem 86 opposite the end fittedto the drive link 66 there is head 88. Pin head 88 extends radiallyoutwardly from the stem 86. The pivot pin 84 is formed with an axiallyextending through bore, bore 89. Bore 89 extends from the top of the pinstem 86, the portion of the pin fitted to the drive link 66 to andthrough the pin head 88. While not seen it should be understood that thecylindrical inner wall of pivot pin 84 that defines bore 89 is threaded.

Bearing assembly 92, seen best in FIG. 8, includes sleeve shaped innerand outer races 94 and 98, respectively. Inner race 94 is dimensioned tohave a tight slip fit over pin stem 86. Outer race 98 is dimensioned tohave a press fit against the inner cylindrical wall of the body head 48that defines bore 56. It is further noted that races are dimensioned sothat the inner race 94 extends above and below the outer race 98. Tworings of ball bearings 96 provide the rotating interface between theraces 94 and 98. Not identified are the grooves in the surfaces of theraces 94 and 98 in which the ball bearings 96 are seated.

When saw unit 40 is assembled, bearing assembly 92 rotatably holds pin84 and, by extension, drive link 66 to the saw body head 48. Thecomponents are dimensioned so that inner race 94 protrudes both aboveand below saw body head 48. The drive link major surface 72 directedtowards saw body head 48 is disposed against the section of the innerrace 94 that projects above the head 48. Pin head 88 is disposed againstthe section of the inner race 94 that projects below the saw body head48.

A linkage assembly, represented by a bar 65 in FIG. 2, extends from themotor shaft 64 to the drive link stem 68. This linkage assemblytransfers the rotational motion of the motor shaft 64 into motion thatcauses the drive link 66 to oscillate back and forth. More specifically,when motor 62 is actuated, the linkage assembly causes the drive link 66to oscillate back and forth around the top to bottom longitudinal axisthrough pin 84. The structure of the linkage assembly is not part of thepresent invention.

A cap 102, seen best in FIGS. 9 and 10, is moveably mounted to the sawbody 42 above the exposed major surface of drive link 66. Cap 102 isgenerally circular in shape. The cap 102 is formed with a through hole106 that extends top to bottom through the cap. Hole 106 is concentricwith the top-to-bottom axis through the cap. The top of the cap 102 isfurther formed to have a tapered opening 104 that leads into hole 106.

The bottom of the cap 102 is formed with a planar undersurface 112.Three sets of arcuately shaped feet extend downwardly from undersurface112. These feet include the press feet 114 and stop feet 118 that areinterleaved in a common circle. Feet 114 and 118 are arcuately spacedapart from each other. The saw unit 40 is constructed so that each pressfoot 114 is located over a separate one of the channels 80 of theunderlying drive link 66. The components are constructed so that eachpress foot 114 subtends an arc that is less than the arc of theunderlying drive link channel 80. Each stop foot 118 subtends an arcgreater than the arc subtended by a single press foot 114. Thecomponents forming the saw unit 40 are further constructed so that thearc separating adjacent stop feet 118 is greater than the arc of thedrive link channel 80 located between and below the adjacent stop feet.Internal to this arc between adjacent stop feet 118 is one of the pressfeet 114 located between each pair of adjacent stop feet 118 Statedanother way, each stop foot 118 is located above an underlying drivelink island 78. Each stop foot 118 subtends an arc less than the arcsubtended by the underlying island 78. Given that the arcuately adjacentfeet 114 and 118 are spaced from each other, there is a gap 116 betweenthe adjacent feet. Owing to the dimensioning of the drive link islands78 and cap feet 114 and 118, each gap 116 is partially located above anunderlying end section of one of the drive link channels 80. Theremainder of each gap 116 is located above one of the drive link islands78 that defines the perimeter of the channel.

The third set of feet of the cap 102 are arcuately shaped compress feet120. Compress feet 120 also extend downwardly from the cap undersurface112. The compress feet 120 are spaced radially outwardly and apart fromthe circle of press and stop feet 114 and 118, respectively. In terms ofarcuate slice sections of the cap 102, each compress foot 120 is inregistration with a separate one of the press feet 114 or one of thestop feet 118. Each compress foot 120 subtends the same arc as the foot114 or 118 with which the foot 120 is in registration. Each compressfoot 120 is arcuately spaced apart from the adjacent compress feet 120.Feet 114, 118 and 120 all extend down the same distance from capundersurface 112.

A screw 122 and knob 134, seen best in FIG. 3, control the relativeheight of the cap 102 to the drive link 66. Screw 122 has a head 124dimensioned to seat in the tapered opening 104 of cap 102. A shaft 126extends downwardly from the head 124. Shaft 126 is formed with threading(not illustrated). Shaft 126 is dimensioned to extend through the hole106 internal to cap 102 and the bore 89 formed in pivot pin 84. Thescrew shaft threading is engaged with the threading around the pivot pinbore 89. A short cylindrical foot 128 projects from the end of the shaft126 opposite screw head 124. Foot 128 has a diameter less than that ofthe screw shaft 126. When saw unit 40 is assembled, foot 128 projects ashort distance below the pivot pin 84.

Knob 134, seen only in FIGS. 1 and 3, is attached to screw foot 128. Theknob 134 is thus located below the head 48 of the saw body 42. The knob134 rotates the screw 122. The component to which the screw 122 isattached, the pivot pin 84, is held static to the drive link 66.Therefore, the rotation of the screw by the knob 134 results in theraising and lowering of the screw head 124 relative to the drive link66.

The blade 140 of saw assembly 30 of this invention, as seen in FIGS. 11and 12, is a single piece assembly. Blade 140 is shaped to have a body148 that is generally planar in shape. At the proximal end of the bodythe blade has a foot 142. Foot 142 is rounded in shape and has adiameter that is greater than the width of the more distal portions ofthe blade body 148. The outer diameter of the foot 142 is substantiallyequal to the common diameter of the drive link head 70 and cap 102. Aslot 144 extends forward from the proximal end of foot 142. Slot 144 hasa width that allows the slot to receive screw shaft 126. The blade 140is further formed so that slot 144 opens up into a hole 146 that extendsthrough the opposed planar faces of the blade foot 142. Hole 146,exclusive of any lock tooth 150 disposed therein, is circular in shapeand has a diameter greater than the width across slot 144 that defines aperimeter portion.

Blade 140 is further formed to have lock teeth 150 that extend inwardlyfrom the portion of the foot that defines the outer perimeter of hole146. Each lock tooth 150 has a body 152 that is approximately in theshape of a truncated isosceles triangle. The bodies 152 of the lockteeth have the same top to bottom thickness T1 as the top to bottomthickness T2 of the blade body 148. The thickness T1 across each body152 of each tooth 150 may generally decrease as the tooth extendsinwardly toward the center of the hole. The portions of the teeth 150closest to the center of hole 146 are rounded to define a circle that isconcentric with the hole. A wing 154 projects, i.e., extends, arcuatelyoutwardly from the each of the opposed side surfaces of the tooth body152. Each wing 154 is formed from two opposed tapered surfaces. Thus,the thickness T1 across opposed faces of the body 152 of a lock tooth150 is generally constant along the tooth body 152. The thickness T3 ofeach tooth wing 154 decreases along lines perpendicular to the linealong which the tooth body 152 extends inwardly towards the center ofhole 146. In the illustrated version of the invention, the radiallyoutermost portion of each tooth wing 154 is spaced inwardly from theperimeter edge of the foot that defines the outer perimeter of hole 146.Given that each wing 154 is spaced from the adjacent perimeter of foot142, it should be appreciated there is a tooth void space 156 betweenthe foot and the wing. The components forming the saw assembly 30 ofthis invention are further dimensioned so that the parallel faces of thetooth bodies 152 have a side-to-side width that is both less than thewidth across a channel 80 formed in the drive link and greater than thewidth across a press foot 114 integral with the cap 102.

The blade 140 is further formed so that cutting teeth 158 extend forwardfrom the distal end of the blade body 148. Cutting teeth 158 aredesigned to, when the blade 148 is oscillated, remove the tissue againstwhich the teeth 158 are applied. The geometry of the cutting teeth 158is not part of the present invention.

While blade 140 is a single piece assembly, there are differences in thecharacteristics of the features of the blade. More specifically, thelock teeth 150 are formed from material that is relatively soft,relatively ductile. This material typically, but not always, has amaximum hardness in the Rockwell B Range. The blade body 148, includingcutting teeth 158, are formed from material harder than the materialfrom which the lock teeth 150 are formed. Typically, the blade body andteeth are typically, but not always, formed from material that has ahardness in the Rockwell C Range.

One means of so fabricating the blade is to form the whole of the blade,the foot 142, the body 148, the lock teeth 150 and the cutting teeth 158out of a single piece of hard metal. After the blade is so shaped, thelock teeth 150 are subjected to a further processing to soften the teeth150, increase their ductility. In one such process, the blade is formedfrom stainless steel. Once the blade 140 is formed, the lock teeth 150are subjected to a localized annealing process. For example, the lockteeth 150 can be so annealed by directed a laser beam to the surface ofthe teeth. The photonic energy of the laser beam heats the teeth 150 totheir annealing temperature. Once the lock teeth 150 are heated to theannealing temperature, the lock teeth are allowed to cool at arelatively slow rate. Often the cooling is at a controlled rate. Giventhat the relatively low thermal conductivity of the stainless steel, theheat generated by this remains localized. The heat does not thereforeresult in the undesired softening of the remainder of the blade 140. Asa result of this annealing process, the metal forming the lock teeth 150becomes softer, more ductile, than the material forming the rest of theblade 140.

A second means to so form the blade is described with reference to FIG.11A. The blade 140 a, is formed with a body, in FIG. 11A, body 148 a,including the foot 142 a and cutting teeth (not seen) out of therelatively hard material. Foot 142 a is formed with a through hole 143.A washer like member 145 formed from more ductile material is welded orotherwise secured to the through hole formed in the foot 142. Thiswasher like member 145 is formed to have the blade lock teeth 150 a.

A saw assembly 30 of this invention is readied for use by coupling theblade 140 to the saw unit 40. To prepare for this operation, knob 134 isrotated to cause screw head 124 to move to the position where the screwhead is spaced from the drive link 66. This allows cap 102 to belikewise be moved upwardly away from the drive link 66. When the sawunit 40 is in this state, the saw unit is in the load or unlocked state.

Once the saw unit 40 is in the unlocked state, the cap 102 is moved awayfrom the drive link 66 a sufficient distance, blade foot 142 is seatedbetween the drive link head 70 and the underside of the cap 102. Thepresence of slot 144 in the blade foot 142 facilitates the insertion ofthe blade around screw 122. The saw unit and blade are placed inregistration with each other as seen in FIG. 13. The blade lock teeth150 are seated over the channels 80 formed on the drive link head 70 sothat each the wings 154 of each tooth 150 rest on the edges of theadjacent and spaced apart islands 78. Thus, the portion of the tooth 150between the wings 154 is thus disposed in the channel 80 between theislands 78. The cap 102 is positioned so that each press foot 114 isdisposed over the face of the tooth body 152 opposite the face that isdisposed in the underlying drive link channel 80.

Once the components of saw assembly 30 are so aligned, knob 134 isrotated to place the saw unit 40 in the run or locked state.Specifically, the knob 134 is rotated to lower screw 122 and, byextension, cap 102. As the cap 102 is lowered, the press feet 114 pressagainst underlying blade lock teeth 150. Since the drive link 66 isstatic, the drive link head 70, including islands 78 function as astatic anvil. Cap 102, having press feet 114, functions as a press.Owing to the ductile nature of the lock teeth 150, the movement of thepress feet towards the drive link results in the teeth deforming betweenthe drive link and the cap. As seen by reference to FIGS. 14 and 15, theoverlying press foot 114 presses against the tooth main body to push thetooth into the underlying channel 80 in the drive link. In FIG. 15, theperimeters of feet 114, 118 and 120 are depicted as dashed lines. Cap102 thus functions as the press and the faces of the press feet 114 arethus the press surfaces of the cap 102. The movement of the press feet114 causes the tooth wings 154, which are thinner than the adjacenttooth main body 152, to bend around the edges around the perimeter ofthe islands 78. Once the locking teeth 150 seat against the underlyingportion of the link main surface that defines the bases of the channels80, the continued motion of the press feet causes the portions of theteeth main body adjacent the edges of the press feet to bend aroundthese edges. Thus, as seen in FIG. 14, the wing portions 154 of eachtooth as well as a small sections of the tooth body 152 adjacent thewings moves are bent into the gaps 116 between the press feet 114 andthe adjacent stop feet 118.

Cap 102 is lowered against the drive link until the stop feet 118 abutthe underlying islands 78 integral with the drive link 66. In FIG. 15,to minimize confusion, the islands 78 against which feet 118 abut arenot shown. Once the cap 102 is so positioned, the saw unit can beconsidered in the run or locked state.

A further effect of the lowering of cap 102 is that, as seen in FIG. 15,the compress feet 120 bear against the blade foot 142. As a consequenceof the press feet 114 pushing the locking teeth 150 into the channels 80and the compress feet 120 pushing against the blade foot 142, the bladefoot is pushed against circular section of the drive link major surface72 located radially outwardly of islands 78. The blade foot 142 is thuscompressed by the drive link major surface 72 and the opposed capcompress feet 120.

As a result of the locking of the blade 140 to the saw unit 40, theblade foot 142 is more than compressed between the drive link 66 and cap102. The deformation of the blade lock teeth 150 around the adjacentcomponents of the drive link and cap essentially make the drive link,the cap and the blade a single piece assembly. There is no clearancebetween the drive link 66 and the saw blade 140. When the drive link 66is oscillated, blade 140 oscillates as one with the drive link 66. Thereis essentially negligible, if any, movement of the blade 140 relative tothe drive link and cap. The undesirable effects associated with saw unitcomponents 66 and 102 and the blade 140 moving relative to each otherare essentially eliminated.

These undesirable effects include the movement of the blade relative tothe saw that can adversely affect the precision of the cuts made be theblade. Still another undesirable effect that is essentially eliminatedis the wear on the saw unit that results from the blade slap. A furtherundesirable effect this invention reduces if not eliminates is thefrictionally induced heating that can occur as a result of the movementof the blade relative to the saw unit. Furthermore, since the blade 140for all intents and purposes moves in unison with the saw couplingassembly, during each phase of an oscillatory cycle, the blade undergoesessentially the same arcuate sweep as the coupling assembly. Thisensures that, in each sweep a tooth of the blade will sweep to at leastthe location of the adjacent tooth at the start of the sweep. Thesweeping of the tooth along this arc increases the likelihood that, inthe sweep all the bone between the teeth was, in the sweep sheared away.The removal of all this bone in a single sweep can enhance theefficiency of the cutting process.

A further advantage is due to the fact that, because the blade 140 isfirmly attached to the coupling assembly, there is little, if any, whip,oscillation of the blade outside of the plane of the cut. This meansthat when the blade is initially applied against bone, the blade can beused to form an initial cut that is thinner than the cut that issometimes formed when the blade engages in whip motion. Since thisinitial cut is thinner, the surgeon can use a blade that is thicker thanthe blade the surgeon may otherwise use to form the cut. A benefit ofusing this thicker blade is that this blade will inherently be stifferthan a thinner blade. This is beneficial because as the blade isadvanced deeper into the bone the stiffness of the blade reduces theextent to which any blade flexure adversely affects the precision of thecut.

Another feature of this invention is that blade is not only compressedbetween the drive link and the press feet 114. The blade is alsocompressed between the drive link major surface 72 and the cap compressfeet 120. This substantially reduces the likelihood that, if the pressfeet and drive link fail to collectively hold the blade lock teeth 150to the saw unit 40, the blade will rapidly work free of the saw unit.

A further benefit of this invention, is that blades of differentthicknesses can be clamped between the drive link 66 and the cap 102.The primary design criteria in providing a saw unit of this inventionable to accept these different blades is that the screw should allow thecap to move above the blade a sufficient height so a blade having thelargest thickness for use with the saw unit can be inserted between thedrive link and the cap.

FIG. 16 is directed to an alternative saw unit 40 a of this invention.The majority of the components of saw unit 40 a are identical to thecomponents of first described saw unit 40. These components are notredescribed. Instead of being provided with a knob to raise and lowerscrew 122, saw unit 40 a has an arm 170. Arm 170 is pivotally attachedto the foot 128 integral with the screw 122.

This construction of the invention has a further benefit by selectiveforming the pitch of the threading integral with pivot pin 84 and screw122. Specifically, the saw unit 40 a can be constructed so that theorientation of the arm relative to the saw body 42 serves as an indiciaregarding whether or not the saw unit is in the fully locked/run state.For example, in some versions of the invention, the components can bearranged so that when the saw unit 40 a is so locked arm 170 is parallelwith the longitudinal axis of the saw body 42.

In more preferred versions of this construction of the invention, theorientation of the arm 170 serves as both an indication of the run orload state of the saw unit 40 a and the type of blade 140 mounted to thesaw unit. For example in some versions of the invention, when a bladethat has a relatively large top face (e.g., face 186) to bottom face(e.g., face 182) thickness T2 is fully locked to saw unit 40 a the arm170 is both parallel to the longitudinal axis of the saw body 42 and ispointed distally forward. When a blade with a relatively thin top face(e.g., face 186) to bottom face (e.g., face 182) thickness T2 is fittedto the saw unit 40 a, an extra half turn or one and half turns of thescrew may be needed to lock the blade. When such a blade is so mounted,the arm 170 will be aligned with the longitudinal axis of the saw body42 and point proximally rearward.

It should be understood that if the arm 170 points forward when the sawis initially placed in the lock state, the arm 170 may extend below theblade 140. This could require the pivoting of the arm proximallyrearward to ensure the full insertion of the blade.

FIG. 17 depicts a portion of an alternative blade 140 b of thisinvention. Blade 140 b contains many of the same features of blade 140.To avoid redundancy these features are neither redescribed nor againillustrated. The difference between blades 140 and 140 b concerns theshape of the locking tooth. Blade 140 b has lock teeth 180, one of whichis seen in cross section in FIG. 17. In cross section, a lock tooth 180can be considered trapezoidal in shape. The tooth 180 has opposedparallel lower and upper, i.e., bottom and top, faces 182 and 186,respectively. Lower face 182 is shorter in length than upper face 186.Tapered side surfaces 184 extend upwardly from the opposed ends of thelower face. Side surfaces 184 extend to the ends of the adjacent upperface 186. The teeth 180 are formed so the opposed side surfaces of eachtooth are symmetric. Side surfaces 184 and outer sections of upper face186 opposed to the side surfaces thus form the outer surfaces of thewings of lock tooth 180.

A benefit of blade 140 b over blade 140 is that it may be moreeconomical to provide a blade with teeth 180 than with teeth 150. Whenblade 140 b is provided, care must be taken to ensure that the blade isorientated so that the teeth bottom surfaces seat in the channels 80between drive link islands 78.

The foregoing is directed to specific versions of the invention. Theinvention may have features different from what has been described.

For example, the features of the different versions of the invention maybe incorporated together.

Further, while the described saw of this invention is a sagittal saw,this invention is not limited to sagittal saws. This invention may beemployed as part of reciprocating surgical saw. A reciprocating surgicalsaw consists of a saw unit and complementary blade that are arranged sothat when the saw unit is actuated, the blade moves back and forth alonga path of travel identical or close to being parallel to thelongitudinal axis of the blade. The saw assembly of this invention mayalso be constructed as an oscillating saw. An oscillating saw is a sawdesigned to pivot a blade around an axis that extends along the axis ofthe saw unit. For the purposes of this invention, since each of theblades repetitively move back and forth, the saw that so cycles theblade is consider to reciprocate the blade back and forth. Anotherversion of the saw unit of this invention is an acetabular cup remover.An acetabular cup remover, as implied by its name, is a specialized sawused to remove a previously implanted artificial acetabular cup. For thepurposes of this invention, since each of the blades is repeatedlycycled back and forth, the saw that so cycles the blade is consider toreciprocate the blade back and forth.

Just as this invention is not limited to a particular type of saw, thesaw unit is not limited to saw units having electrically powered motors.In alternative versions of the invention, the motor may be ahydraulically or pneumatically driven motor or actuator. If the saw unitincludes an electrically driven motor or actuator, it may be possible toattach a battery to the saw unit in order to provide the current neededto actuate the motor.

The described saw unit 40 of this invention is a micro sagittal saw.This saw assembly of this invention may be part of what is referred toas a heavy duty surgical saw. A heavy duty surgical saw is designed toremove large sections of tissue such as the bone of the leg. This is thetype of saw disclosed in the previously incorporated by reference U.S.Pat. No. 8,100,912/PCT Pub. No. WO 2007/011542. Often a heavy dutysurgical saw unit looks different than the elongated saw unit of FIG. 1.More specifically, a heavy duty surgical saw is often pistol shaped. Thesaw has a handgrip and barrel that typically extend forward from thehandgrip. The motor is disposed in the handgrip or the barrel. The sawhead extends forward from the distal end of the barrel.

The various assemblies of this invention may vary from what has beendescribed. For example, the clamping assembly that urges the press feetthe anvil may not always include a threaded screw. In some versions ofthis invention, a rod able to move relative to the head of the saw unitperforms this function. The rod is moved between the run and loadpositions by a manual actuating caroming system. The Applicant's U.S.Pat. No. 7,704,254/PCT Pub. No. WO 2007/030793, the contents of whichare incorporated herein by reference disclose how a rod may be somounted to a saw head. In some versions of the invention, the assemblythat moves the press against the anvil may not have a moving componentthat extends through the blade. Thus, in some versions of the invention,the press may be a plate located over the face of the blade opposite theface directed to the anvil. One or more linkage members located aroundthe outer surface of the blade connect the press plate to the rest ofthe saw unit. These linkage members are actuated to urge the plateagainst the blade (into the run position) or away from the blade (intothe load position).

In some versions of the invention the components forming the anvil andpress are formed with complementary features to facilitate theregistration of these components when the saw head is moved between thelocked and load states. For example, one of the cap or the drive linkmay be provided with a pin. The other of the drive link or cap isprovided with a bore for receiving the pin. The seating of the pin inthe bore ensures the registration of the cap feet to the underlyinganvil of the drive link.

Further, there is no requirement that, relative to gravity reference,the press feet, when moving towards the blade and the anvil movedownwardly in the plane of gravity. In some versions of the invention,when the press feet are moved towards the blade and anvil, the memberthat includes the press fit may move in any direction relative togravity reference plane. Thus while in the primary version of thisinvention the press feet carrying press is a cap, it is understood thatthis press may not always be located above the anvil. In alternativeconstructions of the invention, this press, relative the gravityreference plane be located to the side or below the anvil.

It should likewise be understood that the anvil and press of thisinvention may have alternative constructions. For example, there is norequirement that in all versions of the invention, the press be providedwith compress feet that function as the backup features to hold theblade to the saw unit. In some versions of the invention either one ofthe anvil or press is provided with protruding features. Thecomplementary blade is provided with both the lock teeth and throughopenings. When the blade is mounted to the saw unit, the blade ispositioned so that the protruding features associated with the saw unitseat in the openings formed in the blade. The seating of the protrudingfeatures in the blade functions as the backup assembly thatsubstantially eliminates the likelihood that the blade can work free ofthe saw unit. In some versions of the invention, the saw unit and bladedo not have any features that provide a redundant lock of the blade tothe saw unit.

It is similarly within the scope of this invention that the saw unithave components analogous to the compress feet but no components similarto the stop feet. In some versions of the invention, componentsfunctionally equivalent to both the stop feet and the compress feet maybe omitted. In some versions of the invention, a press foot and acompress foot may be different sections of a single component. In someversions of the invention, a stop foot and a compress foot may bedifferent sections of a single component.

Some saw units and blades of this assembly may be provided so that whenthe saw unit press feet coin the blade lock teeth, the press feetpartially or fully penetrate a portion of the lock teeth. It is furthercontemplated that in most versions of the invention the blade will haveplural deformable lock teeth and the saw unit has one or more featuresable to deform these teeth. However, it is also within the scope of thisinvention that the blade have a single deformable lock tooth and the sawunit has a single press foot for deforming the lock tooth. Likewise,while often preferable, there is no requirement that in all versions ofthe invention, that the press deforms the lock teeth so that the teeth,when deformed, abut the underlying base surface of the anvil. In FIG. 14these are the portions of major surface 72 that defines the bases ofchannels 80.

Variations in the blade of this invention are also possible. Forexample, it should be understood that this invention is not limited tothe disclosed feature of where the blade lock teeth are arranged arounda circle. FIG. 18 illustrates an alternative blade 202 of thisinvention. Blade 202 is a reciprocating saw blade. Blade 202 has a body204 with opposed proximal and distal sections 206 and 208, respectively.The blade 202 is formed with cutting teeth 228 that extend outwardlyfrom a side surface of the blade distal section 208.

Plural lock teeth 210, 214 and 218 extend from the opposed sides of theblade proximal section 206. Lock teeth 210, 214 and 218 thus extendoutwardly from the perimeter edges of the blade body. In the illustratedversion of the invention the lock teeth 210, 214 and 218 aresymmetrically arranged around the proximal to distal longitudinal axisalong the blade body 204. Lock teeth 210, 214 and 218 are more ductile,more prone to deformation, when a force is applied then the blade body204, especially the portion of the body that defines the cutting teeth228.

Each lock tooth 210, 214 and 218 has a main body 220, only twoidentified. At least one tapered wing extends outwardly from the mainbody of each lock tooth 210, 214 and 218. In the illustrated version ofthe invention, a single tapered wing 212 extends distally forward fromthe body of each lock tooth 210. Two tapered wings 216 extend outwardlyfrom the opposed sides of each lock tooth 214. A single tapered wing 222extends proximally from the side of each lock tooth 218. It should beunderstood that FIG. 18 illustrates another feature of this invention,there is no requirement that each lock tooth have two opposed taperedwings. Blade 202 further illustrates another aspect of this invention.Specifically, blade 202 is further designed so that the outer edges ofthe tapered wings of the lock teeth are parallel to the outer edges ofthe bodies of the lock teeth from which the wings extend. In someversions of the invention, the lock teeth may be shaped so thatextending away from the section of the perimeter of the blade from whichthe teeth extend, the edges of the tapered wings extend outwardly fromthe adjacent tooth body.

Likewise, it should be appreciated that there is no requirement that inall versions of the blade the lock teeth project outwardly from the moreproximal sections of the blade body. Similarly, in versions of theinvention where the blade has a foot with inwardly projecting lockteeth, the foot may have a width less than the width of the more distalsections of the blade body. Likewise, the lock teeth may be arranged toproject proximally into space adjacent the proximal end of the blade.

Further, it should be understood that in some versions of the invention,one or more of the lock teeth may not have tapered sections. In someversions of the invention the wing portions of the teeth may simply bethinner in cross sectional thickness than the portion of the toothbodies from which the wings extend. In some versions of the invention,the lock teeth may be of constant cross sectional thickness along thewhole of the teeth. Likewise, in some versions of the invention, the topto bottom thickness of the blade lock teeth may not equal the top tobottom thickness of the blade body. In many versions of the invention,the blade locking teeth may be thinner than the blade body. There can beversions of the invention wherein the thickness of the blade lockingteeth is greater than that of the blade body.

Saw blade 202 is further designed so that lock teeth wings 212, 216 and220 are spaced away from the perimeter edge of the portion of the bladebody 204 from which the bodies of teeth 210, 214 and 218 extend. Thusthere is a tooth void space 219, a gap, between each wing and theadjacent perimeter of the blade body. It should be understood thatspacing of the wings away from the perimeter of the blade body minimizesthe force needed to deform, coin, the wings when the anvil and press arebrought together. It is within the scope of this invention that in someversions of the blade the reduced cross sectional thickness portions ofthe lock teeth extend from the perimeter portions of the associatedblade bodies. In some embodiments of these versions of the invention,the one or more lock teeth do not have section of constant thickness.Thus, in some versions of the invention, there is no break, noseparation, between one or more of the lock teeth and the adjacentperimeter portion of the blade body from which the teeth extend.

Likewise, it is within the scope of this invention that blade will havelock teeth having different shapes and or dimensions. For example, thereis no requirement that in all versions of the invention the lock tooth(or teeth) project outwardly of the adjacent edge of the blade body.FIG. 19 illustrates another sagittal saw blade 246 of this invention.Blade 246 includes a body 250. The body 250 has a proximal section 258and a distal section 260 located forward of the proximal section. Bodydistal section 260 has a side-to-side width greater than that of theproximal section 258. Cutting teeth 262 extend forward from the bodydistal section 260.

Blade body 250 has a single lock tooth 252. Lock tooth 252 is generallyU-shaped. The lock tooth 252 is formed so as to have a base section 254integral with and located immediately proximal to the proximal end ofthe body proximal section 258. The base section 254 of the lock tooth252 thus forms the proximal end of the blade 246. Two arms 256, alsopart of lock tooth 252, extend distally forward from the opposed ends ofthe base section 254. The perimeter of each arm 256 integral with thelock tooth 252 is flush with perimeter of the portion of the baseproximal section 258 immediately forward of the arm.

The lock tooth 252 may be shaped to have an outer perimeter section 257.The outer perimeter section 257 of the tooth 252 has a thickness lessthan that of the section of the tooth 252 located inward of theperimeter section. In some versions of the invention, this perimetersection 257 is tapered relative to the rest of the tooth 252. In otherversions of invention, the perimeter section 257 is stepped inwardlyrelative to the rest of the tooth 252.

Thus, it should be understood that a blade of this invention may beconstructed so the perimeter of the lock tooth is flush with theperimeter of the adjacent section of the blade with which the tooth isassociated. In still other versions of the invention, the blade isshaped so the perimeter of the lock tooth is located inwardly of theperimeter of the section of the blade with which the tooth isassociated.

Alternative versions may be employed to form a blade of this inventionout of single metal workpiece. For example, it is within the scope ofthis invention, that the whole of the blade, the lock tooth (or teeth)the blade body and the cutting teeth are formed out of material that isrelatively soft. Then portions of the blade other than the lock teethare selectively hardened.

One means of so manufacturing the blade is described by reference to theflow chart of FIG. 20. Initially, the blade or, more often pluralblades, are cut from a relatively soft metal, step 280. One such metalis a 300 Series Stainless Steel such as a 316L Stainless Steel. Thissheet has a thickness of approximately 0.4 mm. The blades are laser cut.In this cutting process, the basic perimeters of the cutting teeth andthe blade body and formed. As part of this process, the lock teeth arepartially shaped. More specifically the stock from which the blade isformed is shaped so as to define the outer perimeters of the lock teeth.

An optional part of step 280 is the machine grinding of the partiallyformed blade so as to sharpen the edges of the cutting teeth.

In a step 282 the whole of the blade is hardened. In one version of thismethod of the invention, the blade is hardened by diffusing a hardeningagent into the blade. This agent is diffused into the blade below thesurface of the blade. One hardening agent that can be diffused into theblade is carbon. For example, in one diffusion process, the blade isheated to a temperature between 400 and 600° C. Carbon is diffused intothe whole of the blade to a depth of between 10 and 50 μm. One suchprocess is the process of Kolsterising that is performed Bodycote plc ofMacclesfield, Cheshire, United Kingdom. As a result of this diffusion ofmaterial into the blade, the blade has a hardened outer layer. Thishardened outer layer extends to and is part of the lock teeth.

Once the blade is hardened, in a step 284, sections of the hardenedlayer that are parts of the lock teeth are removed. For example, whenthe blade of FIG. 21 is fabricated, material is removed to define thewings 154 b. The blade 140 b of FIG. 21 is understood to be a variationof blade 140 of FIG. 11. The removal of this material removes thesections of the hardened layer that would have been above the wings 154b. The removal of material in step 284 may be accomplished byelectro-discharge machining or grinding.

It should be understood that in this method of manufacture the bodies152 b of the lock teeth 150 b retain their hardened outer layers. InFIG. 21, the hardened outer layer is represented by the stippling thatextends of the blade body 148 b as well as the bodies 152 b of the lockteeth 150 b. The absence of the stippling of the wings 154 a of the lockteeth 150 b represents that these sections of the lock teeth do notinclude the hardened outer layers. Thus, in these versions of theinvention, while sections of the lock teeth 150 b are relativelyductile, other sections of the lock teeth may be as hard the cuttingteeth.

Once the blade is fully shaped, the blade is cleaned, sterilized andpackaged, step 288. Upon the complete of step 288, the blade is readyfor shipment and eventual use.

It should be understood that the method of FIG. 20 may be used tofabricate of a blade of this invention wherein the lock teeth have aconstant thickness. In order to manufacture this version of the blade, aversion of step 284 is executed so as to remove the hardened layers overthe whole of each lock tooth.

In variations of the method of manufacture of FIG. 20, the hardenedlayer may be removed by laser etching, grinding or the selectiveapplication of an abrasive material against the lock teeth.

In a variation of this method of manufacture, the whole of the blade isformed. A mask is deposited over the sections of the lock teeth that areto remain relatively ductile. Once the mask is formed, the hardeningagent is diffused into the blade. The sections of the blade into whichthe hardening agent is diffused thus develop a hardened outer layer. Themask prevents the hardening agent from diffusing into the mask section(or sections) of the lock teeth. After the mask is removed, thesesections of the lock teeth are thus more ductile than at least thecutting teeth of the blade.

In some versions of this method of manufacture of this invention, theremoval of the portions of the lock teeth to form the wings or otherreduced thickness sections of the lock teeth is performed before thehardening agent is diffused in the blade so as to form the hardenedouter layer. In other versions of this method of manufacture, after thehardening process is completed, the blade is subjected to the finalshaping to form the reduced thickness sections of the lock teeth.

Other processes may be employed to harden at least the cutting teeth ofthe blade while leaving the lock teeth relatively soft and ductile. Inan alternative process, the sections of the blade to be hardened arehardened by bombarding these sections of the blade with nitrogen ions.Alternatively, once the blade is formed a coating may be applied to atleast the cutting teeth to harden these teeth relative to the lockteeth. One coating that can be applied is titanium nitride coating. Analternatively hardening coating that can be applied is a diamond likecarbon coating.

In a variation of this process, the hardened coating is applied to thewhole of the blade. The coating is then removed from the sections of thelock teeth that should be more ductile than the cutting teeth. The sameprocess, electro-discharge machining, laser etching, grinding orabrasive application used to remove the hardened diffused layer may beemployed to selectively remove the hardened coating.

Alternatively, when a coating is applied to harden at least the cuttingteeth of the blade, a mask is applied to the sections of the blade thatis not be provided with the coating. Once the coating process iscompleted, the mask is removed.

Another means to selectively harden at least the cutting teeth of theblade so they are harder than the lock tooth (or teeth) is a selectiveheating process. In a selectively hardening process, a laser istypically applied to the blade to only heat the portions of the blade tobe hardened. The photonic energy of the laser is used to heat theportions of the blade to be hardened to a temperature that is higherthan the annealing temperature of the material. The heated portion (orportions) of the blade are cooled. This cooling is performed at a ratethat is typically faster than the rate of cooling for an annealingprocess. As a result of this rapid cooling, the heated portion (orportions) of the blade is (are) locked into a state in which it (they)are harder than prior to the heating.

From the above it should be clear that in some versions of theinvention, the blade is fabricated so that the lock tooth (or teeth) andbody are of the same hardness and only the cutting teeth is harder thanthe lock tooth (or teeth). Likewise, in some versions of the invention,the blade may be formed so sections of the blade body close to thecutting teeth are relatively hard and sections the blade body close tothe lock tooth (or teeth) are softer.

For the purposes of this invention it is understood that a rasp isconsidered a species of a saw blade. A rasp is a file like cuttingattachment. A rasp is typically, but not always, reciprocated back andforth along a line collinear with the longitudinal axis of the body ofthe rasp. A rasp 202 a is generally seen in FIG. 18A. The rasp 202 a isan alternative version of the reciprocating saw blade 202 of FIG. 18.The rasp 202 a is formed so the teeth 242 extend outwardly from themajor surfaces of the body 204. This is different from a conventionalsaw wherein the teeth project out from the edge surfaces of the bladebody. When this invention is implemented as a rasp, the deformable locktooth or lock teeth 210, 214, 218 extend outwardly from the body of therasp in the vicinity of the proximal end of the body. The cutting teethproject outwardly from the major surfaces body of the rasp at the distalend of the rasp.

It should likewise be appreciated that the shapes of the saw unit anviland press track the arrangement of lock held in place by the anvil andpress. If the lock teeth are arranged linearly, than so are the featuresof the anvil and press that coin the lock teeth.

Also, while the invention is described as primarily for use as surgicalsaw, use of invention is not so restricted. The saw of this inventioncan have other applications. For example, the saw assembly of thisinvention can be used to cut material other than living tissue. Thismaterial includes and is not limited to wood, metal and plastic.

It is therefore an object of the appended claims to cover all suchvariations and modifications that come within the true spirit and scopeof this invention.

1-19. (canceled)
 20. A surgical saw the saw comprising: a body; acoupling assembly mounted to the body and adapted to releasably hold asaw blade to the coupling assembly, the coupling assembly including: ananvil having one of a channel and a press foot, a press having the otherof the press foot and the channel wherein the press foot is capable ofbeing received in the channel, and a clamping assembly connecting thepress and the anvil and selectively moving the press and the anviltowards and away from each other wherein, when the press is broughttowards the anvil, the press foot presses a lock tooth of the saw bladeinto the channel so that the lock tooth is compressed between the anviland the press to coin the lock tooth; and a motor internal to the bodyconnected to the coupling assembly so as to reciprocate the couplingassembly and likewise reciprocate the saw blade held by the couplingassembly.
 21. The surgical saw of claim 20, wherein: the channel isdefined by a space between two islands; and a stop foot is spaced fromand adjacent to the press foot and the stop foot is positioned to seatagainst one of the islands when the press foot presses the lock tooth ofthe blade into the channel.
 22. The surgical saw of claim 20, wherein acompress foot is spaced from and adjacent to the press foot and ispositioned to press against the blade when the press foot presses thelock tooth of the blade into the channel.
 23. The surgical saw of claim20, wherein the press is a cap disposed over the anvil and the pressfoot extends outwardly from a surface of the cap.
 24. The surgical sawof claim 20, wherein actuation of the motor reciprocates the couplingassembly around an axis that extends through the coupling assembly toreciprocate the saw blade around an axis that extends through a plane ofthe blade.
 25. The surgical saw of claim 20, wherein the clampingassembly comprises: a threaded screw having a screw head and the screwhead engaging one of the anvil and the press; and a pivot pin having athreaded bore and having a pin head engaging the other of the press andthe anvil, wherein the threaded screw is threaded into the pivot pin andthe screw and the pivot pin collectively pass through each of the anviland the press and selective rotation of the screw relative to the pinmoves the press and the anvil toward and away from each other.
 26. Thesurgical saw of claim 25, wherein the screw includes a compress foot andone of a knob and a pivotable arm is fixed to the compress foot forunitary rotation with the screw.
 27. The surgical saw of claim 26,wherein the pivotable arm is pivotably fixed to the compress foot andthe pivotable arm has a locked position substantially parallel with anaxis of the body in a run state.
 28. The surgical saw of claim 26,wherein the pivotable arm is pivotably fixed to the compress foot andthe pivotable arm has a locked position substantially parallel with anaxis of the body and extends in a proximal direction in a run state.